.\"-
.\" Copyright (c) 2001 Miodrag Vallat.
.\" Copyright (c) 2005 Marius Strobl <marius@FreeBSD.org>
.\" All rights reserved.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
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.\"	from: OpenBSD: pcons.4,v 1.4 2003/06/02 16:16:26 miod Exp
.\"
.Dd January 16, 2021
.Dt OFW_CONSOLE 4 powerpc
.Os
.Sh NAME
.Nm ofw_console
.Nd "Open Firmware console"
.Sh SYNOPSIS
.Cd "cpu AIM"
.Cd "options OFWCONS_POLL_HZ=N"
.Pp
.Cd "options KDB"
.Cd "options DDB"
.Cd "options ALT_BREAK_TO_DEBUGGER"
.Sh DESCRIPTION
The
.Nm
driver provides a simple text console,
using the Open Firmware services for input and output.
It will use the Open Firmware console devices set via the
.Va input-device
and
.Va output-device
variables.
.Pp
This driver is deprecated and only provided as a fallback console mechanism
if the real console hardware can not be driven by
.Fx .
.Pp
In case the
.Nm
console appears to work too slowly, its responsiveness probably can be improved
by including
.Cd "options OFWCONS_POLL_HZ=N" .
When omitted,
.Dv OFWCONS_POLL_HZ
defaults to 4.
For example, on
.Tn Sun Ultra 2
a value of 20 or higher works best.
Too high values, on the other hand, can cause
.Nm
to unnecessarily consume CPU.
.Sh FILES
.Bl -tag -width ".Pa /dev/keyboard" -compact
.It Pa /dev/console
.It Pa /dev/keyboard
terminal input device in case the console input device is the keyboard
.It Pa /dev/screen
terminal output device in case the console output device is the screen
.It Pa /dev/tty[a-z]
terminal device in case both the console input and output device is tty[a-z]
.El
.Sh SEE ALSO
.Xr akbd 4 ,
.Xr powermac_nvram 4 ,
.Xr vt 4
.Sh HISTORY
The
.Nm
driver first appeared in
.Fx 5.0 .
.Sh AUTHORS
The
.Nm
driver was written by
.An Benno Rice Aq Mt benno@FreeBSD.org .
.Sh CAVEATS
Since the Open Firmware will handle BREAK
(or Stop-A)
sequences before
.Nm ,
the preferred way to enter
.Xr ddb 4
when using
.Nm
is to include
.Cd "options ALT_BREAK_TO_DEBUGGER"
in a ddb-enabled kernel, and enter the alternate BREAK sequence
(RETURN TILDE CTRL-b).
.Sh BUGS
The
.Nm
driver also not attach to the hardware resources it actually talks to.
